The present invention relates to a power train controller and control method suitable to facilitate precise driver control of a motorized passenger car with an automatic multigear speed changing transmission
A first prior art power train control system for a passenger car is described in Japanese Published Patent Application No. 117774-1991. In this system the driver can select an economy mode and a power mode operation of the transmission, with the speed change line set faster for the power mode than for the economy mode. The desired speed change characteristics can be selected by manual switch operation.
A second prior art power train control system is described in Japanese Published Patent Application No. 346162-1993. This system introduces fuzzy inference to predict and infer the road conditions from the current operation conditions. The speed change line is modified according to the inferred road conditions, thereby obtaining speed changes such as acceleration and deceleration as desired by the driver to a certain extent.
According to the first prior art mentioned above, there are available speed change characteristics in the power mode where the speed change line is set on the side faster than that of the economy mode, in addition to speed change characteristics in the economy mode which consider only fuel combustion efficiency. Operation performances are also taken into account, though, to a limited extent, with the result that it has failed to cut down fuel costs as expected. The second prior art mentioned above was intended to operate with use of the fuzzy inference to determine the optimum speed change line, but was accompanied by such problems as failure to get speed changes such as acceleration and deceleration, as desired by the driver.
An object of the present invention is to provide a power train controller and control method to ensure operation of an automatic speed change transmission driven car as desired by the driver, in response to the car operating conditions and control functions which are different for different drivers (different driver preferences).
The above noted object of the present invention is attained by preferred embodiments of the present invention which comprise: (1) a control sensor to detect the current vehicle operating conditions and the amount of driver operation, (2) a driver intention prediction means reflecting the driver intention, (3) an operation mode selection means to select the operation mode predicted by the driver intention prediction means from two or more operation modes, (4) a control function selecting means to select at least two control functions according to the mode selected by the operation mode selecting means, and (5) a control amount computing means to compute the control amount of the control actuator, using the signals from the control sensor and control function selecting means.
In preferred embodiments of the invention, three operation modes are provided, namely: (i) economy mode, (ii) sports mode, and (iii) comfortable mode.
When the extra-low fuel cost "economy" operation mode is selected by the driver using the operation mode selecting means, two or more control functions are selected by the control function selecting means, for example, wide-area lockup control to achieve fuel cost reduction (to improve torque transmission efficiency by eliminating torque converter slide), fuel cost speed change control (the speed change point determined so as to operate the engine at the maximum point of the engine efficiency, with consideration given to torque transmission efficiency) and fuel cut control (fuel cut executed during deceleration and speed change), thereby enabling the operation which improves fuel cost efficiency as intended by the driver.
When the "sports" operation mode is selected, the control function selecting means selects such control as high rotation speed change control to change the speed at high rotation speed to improve the sense of acceleration, short speed change time control to prevent reduction in acceleration during speed change, or powerful engine brake control by shift-down around the corner inlet to run around corners at a high speed, thereby providing the operation in the "sports" mode intended by the driver.
When the "comfortable" operation mode is selected, the control function selecting means selects the equi-interval speed change control to make the speed change time intervals equal, smooth speed change control to make speed change time control and shock reduction compatible, or speed change line control to determine the speed change line in conformity to each gradient by inferring the road conditions (gradient, etc.) based on fuzzy theory.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.